The physical mechanism of wave-particle resonances in a curved magnetic field is investigated. Specifically, the energy exchange process between a wave and resonant curvature drifting particles is discussed (i.e., ω∼k⋅Vc, where Vc = v2∥/RcΩ is the curvature drift, Rc is the radius of curvature of the magnetic field, and Ω is the cyclotron frequency). A general expression for the wave damping/growth rate is derived based upon physical arguments. The theory is applied to the lower-hybrid-drift instability and nonlinear consequences are discussed.